(a) Technical Field
The present disclosure relates to a display device and a driving method thereof and, more particularly, to an organic light emitting display and a driving method thereof.
(b) Discussion of Related Art
In general, an active matrix flat panel display includes a plurality of pixels displaying an image, and it displays an image by controlling the luminance of respective pixels based on given display information. Among such active matrix flat panel displays, an organic light emitting display is a self-emissive display device having low power consumption, a wide viewing angle, and a high response speed, so that the organic light emitting display is being spotlighted as a next-generation display device to supplant the liquid crystal display (LCD).
Each pixel of an organic light emitting display includes an organic light emitting element, a driving transistor driving the organic light emitting element, and a switching transistor applying a data voltage to the driving transistor. The transistors are each implemented in the form of a thin film transistor (TFT). The TFTs are classified as a crystalline silicon TFT including a poly-crystalline or micro-crystalline silicon active layer and an amorphous silicon (abbreviated to “a-Si”) active layer.
The a-Si is easily processed due to its low deposition temperature. It is difficult for a TFT adopting a-Si as a channel layer to drive a high current, however, because of its low electron mobility. Additionally, the threshold voltage of an a-Si TFT is apt to be varied as time passes.
On the other hand, although crystalline silicon has high electron mobility, the off-current of a crystalline silicon TFT is so high that vertical crosstalk may be generated.
Accordingly, an a-Si TFT is more suitable for a switching transistor than for a driving transistor, but on the other hand a crystalline silicon TFT is relatively suitable for a driving transistor.
The employment of both the a-Si TFT and the crystalline silicon TFT, however, may complicate the manufacturing process to increase the time and cost.